The pilot was qualified for the flight, and meteorological conditions were favourable for the flight. The pilot had made repairs to one propeller blade. However, the precise nature of the repair could not be determined because that blade was never found. However, the pilot did not seem satisfied with the repair, as a previous repair to the same propeller had not produced the desired results. When the aircraft started to vibrate in flight, all indications are that the pilot tried to come back to the channel and land the ultralight. To that end, he adjusted engine power several times to reduce the vibrations caused by the loss of the propeller blade. As there were several boats on the water, the pilot executed a 180-degree turn to avoid them before setting the ultralight down. The evidence indicates that the aircraft stalled during this low- altitude turn before crashing on the island and catching fire. The following Engineering Branch report was completed: LP 141/95 - Aileron Pushrod Examination.Analysis The pilot was qualified for the flight, and meteorological conditions were favourable for the flight. The pilot had made repairs to one propeller blade. However, the precise nature of the repair could not be determined because that blade was never found. However, the pilot did not seem satisfied with the repair, as a previous repair to the same propeller had not produced the desired results. When the aircraft started to vibrate in flight, all indications are that the pilot tried to come back to the channel and land the ultralight. To that end, he adjusted engine power several times to reduce the vibrations caused by the loss of the propeller blade. As there were several boats on the water, the pilot executed a 180-degree turn to avoid them before setting the ultralight down. The evidence indicates that the aircraft stalled during this low- altitude turn before crashing on the island and catching fire. The following Engineering Branch report was completed: LP 141/95 - Aileron Pushrod Examination. The pilot was qualified for the flight. The pilot repaired one blade of the propeller and seemed unsatisfied with the results. The pilot was authorized to repair the propeller. One propeller blade separated in flight and was not found. The cause of the loss of the propeller blade in flight could not be determined. The wings of the aircraft started to vibrate shortly before the accident. The aircraft stalled in a low-altitude turn and crashed.Findings The pilot was qualified for the flight. The pilot repaired one blade of the propeller and seemed unsatisfied with the results. The pilot was authorized to repair the propeller. One propeller blade separated in flight and was not found. The cause of the loss of the propeller blade in flight could not be determined. The wings of the aircraft started to vibrate shortly before the accident. The aircraft stalled in a low-altitude turn and crashed. The aircraft stalled in a low-altitude turn after one blade separated from the propeller. The repair to the propeller of the ultralight contributed to the accident.Causes and Contributing Factors The aircraft stalled in a low-altitude turn after one blade separated from the propeller. The repair to the propeller of the ultralight contributed to the accident.